Roles of endothelin-1 in regulation of rat hepatic sinusoidal blood flow

Immunoreactivities for big endothelin (ET)-1 and ET-1, and gene expressions for preproET-1mRNA were preferentially seen along the endothelium of interlobular vein (IV) in rat liver vasculature. Rough endoplasmic cisterns and Weibel-Palade (WP) bodies in endothelial cells of IV were immunoreactive for big ET-I and ET-1, respectively. These indicate the involvement of the endothelial cells in synthesis of ET-1, which is in part stored in WP bodies. Since hepatic stellate cells (HSCs) were immunoreactive for ET receptor A and B (ETA and ETB), it is thought that ET-1 receptor-mediated HSC contraction regulates hepatic sinusoidal blood flow. The sarcolemma of smooth muscle cells in IV was also immunoreactive for ETA. This implies that IV, receiving a large amount of the portal blood inflow, participates in pump mechanism toward hepatic sinusoidal circulation in a receptor-mediated paracrine fashion.